The present invention relates to a non-contact IC card system including a non-contact IC card using electromagnetic induction but not having a battery, and to a non-contact IC card.
FIG. 36 illustrates a configuration of this type of conventional non-contact IC card system. In this illustration, numeral 80 designates a non-contact IC card (which will be referred to hereinafter as a card) not containing a battery, while numeral 70 denotes a reader writer (which will be referred to hereinafter as an R/W).
In the card 80, numeral 81 represents an antenna resonance circuit constituting a parallel resonance circuit using an antenna coil 81a and a capacitor 81b, numeral 82 depicts a rectifying circuit comprising rectifying devices 82a and 82b, and numeral 83 signifies an energy storing circuit made up of energy storing capacitors 83a and 83b for storing energy after rectification. FIG. 36 shows an example of full-wave voltage doubler rectifying circuits.
Numeral 84 designates a comparator for detecting the fact that a voltage after rectification exceeds a predetermined value, and numeral 84a signifies a reference power supply for producing the aforesaid predetermined value. In addition, numeral 85 depicts a variable resistive device comprising, for example, an MOSFET transistor and connected in parallel to the antenna resonance circuit 81. This variable resistive device 85, when the comparator 84 detects that the voltage after the rectification exceeds the predetermined value, alters a quality factor Q of the antenna resonance circuit 81 in proportion to the exceeding or extra quantity from the predetermined value.
Numerals 86a and 86b represent output transistors, respectively, numeral 87 designates a transistor drive circuit to be described later, numeral 88 denotes a driver taking an operating condition by a control signal 88a at transmission, and numeral 89 indicates a resistor connected to the output side of this driver.
Numeral 90a depicts a high-potential side level comparator for detecting the fact that the high-potential side amplitude level of the antenna resonance circuit 4 exceeds a predetermined value (for example, Vcc), numeral 90b denotes a low-potential side level comparator for detecting the fact that the low-potential side amplitude level of the antenna resonance circuit 81 falls below a predetermined value (for example, GND), numeral 90c signifies an intermediate level comparator for detecting whether the antenna resonance circuit 81 is above or below a predetermined value (for example, xc2xd Vcc), numeral 91 means a control section, and numeral 92 designates a memory section for data storage.
Meanwhile, in the R/W 70, numeral 71 represents a transmission antenna resonance circuit comprising an antenna coil 71a and a capacitor 71b to constitute a series resonance circuit, numeral 72 denotes a power transmission adjusting resistor for adjusting the magnitude of the power transmission from the R/W 70, numeral 73 depicts a driver, and numeral 74 indicates a modulating circuit comprising an EX-OR circuit, connected to the input side of this driver 73 and made to receive data 74a and a carrier 74b. 
Numeral 75 represents a reception antenna resonance circuit comprising an antenna coil 75a and a capacitor 75b, constituting a parallel resonance circuit, numeral 76 denotes an amplifying circuit for amplifying a signal received, and numeral 77 depicts a demodulating circuit.
Since the power supply varies depending upon the distance between R/W 70 and the card 80, for absorbing this variation, on the card 80 side, the quality factor Q of the antenna resonance circuit 81 is altered on the basis of the voltage after the rectification, thereby stabilizing the voltage induced in the card 80.
When the comparator 84 makes a decision that the voltage after the rectification exceeds the predetermined value, the variable resistive device 85 adjusts the quality factor Q of the antenna resonance circuit 81 so that the quality factor Q decreases correspondingly to the exceeding quantity from the predetermined value. Furthermore, the decrease of Q causes the adjustment of the reception voltage, which leads to the stabilization of the voltage, to be induced in the card 80, against the variation of the distance between the R/W 70 and the card 80.
In addition, a modulation system for data transmission from the card 80 to the R/W 70 also requires less consumption of energy. For this reason, a modulation is made by varying the constant of the antenna resonance circuit 81. A phase modulation system is realized in a manner that the constant of the antenna resonance circuit 81 is changed correspondingly to the variation of data to be transmitted.
In the case of the phase modulation system, the transistor drive circuit 87 generates a 180xc2x0 pulse lasting for a period of a phase of 180xc2x0 when the output data varies. This 180xc2x0 period is determined from the output of the intermediate level comparator 90c. 
Furthermore, in a manner that the output transistor 86a conducts ON/OFF operation in accordance with this 180xc2x0 pulse, the connection/disconnection of the output capacitor 86b to/from the antenna resonance circuit 81 is accomplished so that the resonance frequency of the antenna resonance circuit 81 varies with the variation of data. The connection of the output capacitor 86b to the antenna resonance circuit 81 causes the variation of the circuit constant of the antenna resonance circuit 81.
FIG. 37 is a waveform illustration for explaining the operation. In FIG. 37, (a) indicates data, (b) indicates a carrier, (c) shows a waveform after phase modulation, (d) shows a signal (180xc2x0 pulse) to the base of the transistor 86a at the phase modulation, (e) illustrates a waveform after frequency modulation which will be described later, and (f) illustrates a signal to the base of the transistor 86a when the frequency modulation is conducted.
As shown in (a) to (d) of FIG. 37, when the variation of the output data takes place (variation from an H level to a L level and from the L level to the H level), the frequency is changed for a period of 180xc2x0 and, assuming that this frequency is xc2xd of the original frequency, the two-phase modulation is realized.
That is, as shown in (c) of FIG. 37, the signal after the phase modulation turns in frequency to xc2xd for the period of 180xc2x0 from the variation of data, that is, the period between A and B and the period between C and D, whereupon the phase inverts for the period between B and C.
In addition, taking the phase into consideration rather than the output of the intermediate level comparator 90c, if the output transistor 86a is turned ON/OFF in accordance with the variation itself of the output data from the control section 91, as shown in (e) and (f) of FIG. 37, the frequency modulation is conducted such that the frequency becomes xc2xd.
Still additionally, as another approach, there has been a system in which the output transistor 86a is connected between both the ends of the resonance circuit 81 and both the ends of the resonance circuit 81 is short-circuited at a varying point of the output data for the period of 180xc2x0 to compulsively invert the phase for the PSK modulation, thereby accomplishing high-speed data transmission.
In the above-described conventional non-contact IC card system, the power transmission has been made from the R/W to the card, while the data transmission has been performed in a manner that its power carrier is PSK (Phase Shift Keying)-modulated in accordance with data.
In such a system, if an approach is taken to achieve the improvement of the data transmission rate and the improvement of the communication range simultaneously, since the range of the variation of the frequency of signal to be put to use is wide, the frequency band also becomes wide. Further, since a restriction is imposed according to the wireless telegraphy act, which may be different for every nation, a problem has arisen, for example, in achieving a system which functions to universally achieve the same purpose.
Accordingly, it is an object of the present invention to provide a non-contact IC card system and a non-contact IC card which are capable of improving the data transmission rate and communication range without considerably broadening the frequency band of a signal to be put to use.
This invention provides a non-contact IC card system including an R/W and a non-contact IC card, characterized in that the non-contact IC card comprises a regulator connected to both ends of a resonance circuit having an oscillation frequency identical with a frequency of a power transmission carrier for conducting reception of power and data from the R/W and transmission of data to the R/W, with the regulator stabilizing an operating voltage in the resonance circuit, and switching its characteristic in accordance with transmission data to produce a load variation for conducting data transmission by an AM modulation.
Furthermore, this invention provides a non-contact IC card system including an R/W and a non-contact IC card, characterized in that the non-contact IC card comprises a regulator connected to both ends of a resonance circuit having an oscillation frequency identical with a frequency of a power transmission carrier for conducting reception of power and data from the R/W and transmission of data to the R/W, with the regulator adjusting a voltage across the resonance circuit and giving a directionality in accordance with transmission data in adjusting the voltage across the resonance circuit to conduct data transmission at a frequency different from the power transmission carrier, while the R/W comprises a data reception resonance circuit having a resonance frequency matching with a frequency for the data transmission from the card.
Still furthermore, this invention offers the non-contact IC card system according to claim 2, characterized in that the regulator includes an adjusting section for adjusting the voltage across the resonance circuit and a pair of directionality designating sections for giving a directionality to this adjustment, and the pair of directionality designating sections are alternately operated in accordance with the transmission data so that the directionality is given to the adjustment, while the pair of directionality designating sections are operated simultaneously in accordance with the transmission data so that data transmission is conducted by an AM modulation.
In addition, this invention offers the non-contact IC card system according to claim 2, characterized in that the non-contact IC card further comprises an additional data transmission resonance circuit having an oscillation frequency matching with a frequency for the data transmission, and this data transmission resonance circuit conducts data transmission by obtaining transmission power from electromagnetic coupling with the resonance circuit having the oscillation frequency identical with the power transmission carrier.
Moreover, this invention provides a non-contact IC card system including an R/W and a non-contact IC card, characterized in that the R/W comprises a transmission resonance circuit having a resonance frequency matching with a frequency of a power transmission carrier for conducting power transmission and data transmission and a data reception resonance circuit having a resonance frequency matching with a frequency for data transmission from the non-contact IC card, while the non-contact IC card comprises a reception resonance circuit having a resonance frequency matching with a frequency of the power transmission carrier for conducting reception of power and data from the R/W, a resonance circuit for data transmission to the R/W, having a resonance frequency different from the frequency of the power transmission carrier, and a driver connected to the data transmission resonance circuit and driven by a signal having a lower duty ratio than a transmission carrier for data transmission.
Furthermore, this invention provides a non-contact IC card system including an R/W and a non-contact IC card, characterized in that the R/W comprises a transmission resonance circuit having a resonance frequency matching with a frequency of a power transmission carrier for conducting power transmission and data transmission and a data reception resonance circuit having a resonance frequency matching with a frequency for data transmission from the non-contact IC card, while the non-contact IC card comprises a reception resonance circuit having a resonance frequency matching with a frequency of the power transmission carrier for conducting reception of power and data from the R/W and a data transmission resonance circuit having a resonance frequency different from the frequency of the power transmission carrier and made to obtain transmission power from electromagnetic coupling with the reception resonance circuit.
Still furthermore, this invention provides a non-contact IC card system including an R/W and a non-contact IC card, characterized in that the R/W comprises a transmission resonance circuit having a resonance frequency matching with a frequency of a power transmission carrier for power transmission and a data transmission/reception resonance circuit having a resonance frequency matching with a frequency for data transmission/reception to/from the non-contact IC card, while the non-contact IC card comprises a reception resonance circuit having a resonance frequency matching with the frequency of the power transmission carrier for conducting reception of power from the R/W and a data transmission/reception resonance circuit having a resonance frequency different from the frequency of the power transmission carrier for conducting data transmission/reception to/from the R/W.
Still furthermore, this invention provides a non-contact IC card system including an R/W and a non-contact IC card, characterized in that at least one of the R/W and the non-contact IC card comprises an AM demodulating circuit for converting a reception signal being a carrier AM-modulated by transmission data into a binary signal by comparing the reception signal with a reference value and further for detecting the transmission data by comparing a pulse width of the converted binary signal with a width of a reference pulse feedbacked to vary in accordance with a variation of the pulse width of the converted binary signal.
Still furthermore, this invention provides a non-contact IC card system including an R/W and a non-contact IC card, characterized in that at least one of the R/W and the non-contact IC card comprises a filter for converting a reception signal including a plurality of carriers different in frequency from each other into a binary signal by comparing the reception signal with a reference value and further for extracting a carrier with a desired frequency by comparing a pulse width of the converted binary signal with a width of a reference pulse feedbacked to vary in accordance with a variation of the pulse width of the converted binary signal.
In addition, this invention offers the non-contact IC card system according to any one of claims 1 to 4, characterized by comprising a sub-carrier producing section for dividing a power transmission carrier from the R/W to the non-contact IC card to produce a sub-carrier having a different frequency, with the sub-carrier being modulated by transmission data.
Moreover, this invention provides a non-contact IC card which receives power supply from an R/W and conducts data transmission/reception to/from the R/W, characterized by comprising a regulator connected to both ends of a resonance circuit having an oscillation frequency identical with a frequency of a power transmission carrier for conducting reception of power and data from the R/W and transmission of data to the R/W, with the regulator stabilizing an operating voltage of the resonance circuit and switching its characteristic in accordance with transmission data to generate a load variation so that data transmission is conducted by an AM modulation.
Furthermore, this invention provides a non-contact IC card which receives power supply from an R/W and conducts data transmission/reception to/from the R/W, characterized by comprising a regulator connected to both ends of a resonance circuit having a resonance frequency identical with a frequency of a power transmission carrier for conducting reception of power and data from the R/W and transmission of data to the R/W, with the regulator adjusting a voltage across the resonance circuit and giving a directionality according to transmission data in adjusting the voltage across the resonance circuit to conduct data transmission at a frequency different from the power transmission carrier.
In addition, this invention offers the non-contact IC card, characterized in that the regulator includes an adjusting section for adjusting the voltage across the resonance circuit and a pair of directionality designating sections for giving a directionality to this adjustment, and the pair of directionality designating sections are alternately operated in accordance with the transmission data so that the directionality is given to the adjustment, while the pair of directionality designating sections are operated simultaneously in accordance with the transmission data so that data transmission is conducted by an AM modulation.
Still additionally, this invention offers the non-contact IC card, characterized by further comprising an additional data transmission resonance circuit having an oscillation frequency matching with a frequency for the data transmission, and this data transmission resonance circuit conducts data transmission by obtaining transmission power from electromagnetic coupling with the resonance circuit having the oscillation frequency identical with the power transmission carrier.
Furthermore, this invention provides a non-contact IC card which receives power supply from an R/W and conducts data transmission/reception to/from the R/W, characterized by comprising a reception resonance circuit having a resonance frequency matching with a frequency of a power transmission carrier for conducting reception of power and data from the R/W, a resonance circuit for data transmission to the R/W, having a resonance frequency different from the frequency of the power transmission carrier, and a driver connected to the data transmission resonance circuit and driven by a signal having a lower duty ratio than a transmission carrier for data transmission.
Still furthermore, this invention provides a non-contact IC card which receives power supply from an R/W and conducts data transmission/reception to/from the R/W, characterized by comprising a reception resonance circuit having a resonance frequency matching with a frequency of a power transmission carrier for conducting reception of power and data from the R/W and a data transmission resonance circuit having a resonance frequency different from the frequency of the power transmission carrier and made to obtain transmission power from electromagnetic coupling with the reception resonance circuit.
Still furthermore, this invention provides a non-contact IC card which receives power supply from an R/W and conducts data transmission/reception to/from the R/W, characterized by comprising a reception resonance circuit having a resonance frequency matching with a frequency of a power transmission carrier for reception of power from the R/W and a data transmission/reception resonance circuit having a resonance frequency matching with a frequency for data transmission/reception different from the frequency of the power transmission carrier for conducting data transmission/reception to/from the R/W.
Still furthermore, this invention provides a non-contact IC card which receives power supply from an R/W and conducts data transmission/reception to/from the R/W, characterized by comprising an AM demodulating circuit for converting a reception signal being a carrier AM-modulated by transmission data into a binary signal by comparing the reception signal with a reference value and further for detecting the transmission data by comparing a pulse width of the converted binary signal with a width of a reference pulse feedbacked to vary in accordance with a variation of the pulse width of the converted binary signal.
Still furthermore, this invention provides a non-contact IC card which receives power supply from an R/W and conducts data transmission/reception to/from the R/W, characterized by comprising a filter for converting a reception signal including a plurality of carriers different in frequency from each other into a binary signal by comparing the reception signal with a reference value and further for extracting a carrier with a desired frequency by comparing a pulse width of the converted binary signal with a width of a reference pulse feedbacked to vary in accordance with a variation of the pulse width of the converted binary signal.
Besides, this invention offers the non-contact IC card according to any one of claims 1 to 4, characterized by comprising a sub-carrier producing section for dividing a power transmission carrier from the R/W to the non-contact IC card to produce a sub-carrier having a different frequency, with the sub-carrier being modulated by transmission data.